Regional-scale patterns and drivers of soil CO₂ emissions in steppe ecosystems

Abstract

Soil respiration is a pivotal component of the global carbon cycle, yet the regional-scale variations in CO₂ emissions across steppe ecosystems, especially under anthropogenic nitrogen deposition, remain poorly understood. Here, we investigated soil CO₂ emissions from 30 sites spanning three major steppe regions (Inner Mongolia Plateau, Loess Plateau, and Tibetan Plateau) to elucidate regional patterns and underlying drivers. Our results show that desert steppes emitted 50%−90% less CO₂ than meadow steppes, primarily due to differences in soil organic carbon (SOC). Simulated nitrogen deposition via nitrate ({\mathrm{N}\mathrm{O}}_3^{-}) addition significantly enhanced CO₂ emissions in nitrogen-limited regions (Loess and Tibetan Plateaus), while nitrogen-rich soils (Inner Mongolia Plateau) showed saturation effects. Random forest and partial least squares path modeling (PLSPM) analyses showed that nitrogen availability, climate, and elevation jointly regulated CO₂ fluxes, with distinct regional pathways. These findings highlight the importance of spatial heterogeneity in regulating carbon emissions and suggest region-specific strategies. Protecting high-carbon steppes and regulating nitrogen inputs are vital for mitigating climate feedbacks in China grasslands.

Graphical abstract

Keywords

soil CO₂ emission / steppe ecosystems / nitrogen deposition / regional-scale

Highlight

	● Soil CO2 emissions show distinct regional patterns in steppe ecosystems.
	● Altitude, soil carbon, and nitrogen availability drive regional CO2 emission variability.
	● Nitrogen addition enhances CO2 emissions in nitrogen-limited regions, with saturation effects in nitrogen-rich soils.

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